/**
 * Storage Utility — type-safe wrapper for localStorage and sessionStorage
 * with JSON serialisation, TTL (expiry), versioning, and event emission.
 *
 * @example
 * const storage = createStorage('my-app');
 * storage.set('user', { name: 'Alice' }, { ttl: 60 * 60 * 1000 }); // 1 hour
 * const user = storage.get<User>('user');
 * storage.remove('user');
 */
export interface StorageOptions {
    /** Time-to-live in milliseconds. If set, item expires after this duration. */
    ttl?: number;
    /** Schema version. If stored version differs, item is removed and null returned. */
    version?: number | string;
}
export type StorageType = 'local' | 'session';
declare class TypedStorage {
    private _ns;
    private _store;
    constructor(namespace: string, type?: StorageType);
    private _key;
    /** Set a value with optional TTL and version. */
    set<T>(key: string, value: T, options?: StorageOptions): void;
    /** Get a value. Returns null if missing, expired, or version mismatch. */
    get<T>(key: string, expectedVersion?: number | string): T | null;
    /** Get a value or return the fallback if missing. */
    getOr<T>(key: string, fallback: T, expectedVersion?: number | string): T;
    /** Check if a key exists and is valid (not expired). */
    has(key: string): boolean;
    /** Remove a key. */
    remove(key: string): void;
    /** Remove all keys in this namespace. */
    clear(): void;
    /** Get all keys in this namespace (namespaced prefix stripped). */
    keys(): string[];
    /** Get all valid values in this namespace as a keyed record. */
    getAll<T = unknown>(): Record<string, T>;
    /** Update a value by merging with existing object. */
    merge<T extends object>(key: string, partial: Partial<T>, options?: StorageOptions): void;
    /** Purge all expired entries in this namespace. */
    pruneExpired(): number;
    /** Watch a key for changes from other tabs/windows (localStorage only). */
    watch<T>(key: string, callback: (newValue: T | null, oldValue: T | null) => void): () => void;
    /** Total number of valid (non-expired) items in this namespace. */
    get size(): number;
}
/**
 * Create a namespaced localStorage store.
 * @example
 * const store = createStorage('myapp');
 * store.set('settings', { theme: 'dark' });
 */
export declare function createStorage(namespace?: string, type?: StorageType): TypedStorage;
/** Convenience pre-built stores */
export declare const localStorage: TypedStorage;
export declare const sessionStorage: TypedStorage;
export { TypedStorage };
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